Method of making curved staircase

ABSTRACT

Right-angle braces are formed of two sections of angle iron mitered together. One leg of the brace is adapted to receive the riser of a stair; and the other leg is adapted to receive the tread of the stair. A number of these braces, each designed to define one side of a step in a curved staircase, are mounted on a flat metal bar to form a flat string for the staircase. A similar flat metal bar is place in a jig at the pitch and curvature the finished staircase is intended to assume; and the formed string is placed in the jig with the two flat bars engaging each other throughout their lengths. The two bars are then welded together to form a lamination while in the jig to provide the curved horse for one side of the staircase with the laminated bars retaining the desired curve and pitch after removal from the jig. Another metal horse is similarly formed for the other side of the staircase, but in a separate jig of different curvature. After the two curved horses are installed, the treads and risers are attached to a pair of associated braces by screws inserted from beneath the metal frames.

United States Patent [191 Cirgenski, Jr. et al.

[ 1 May 15,1973

[54] METHOD OF MAKING CURVED STAIRCASE [73] Assignees: Stile-King Stairs, Inc.; Scholz Homes, Inc., both of Toledo, Ohio [22] Filed: Mar. 2, 1970 [21] Appl. No.: 20,261

Related U.S. Application Data [62] Division of Ser. No. 734,413, June 4, 1968, Pat. No.

Primary Examiner-Charles W. Lanham Assistant ExaminerD. C. Crane Attorney Dawson, Tilton, Fallon & Lungmus 57] ABSTRACT Right-angle braces are formed of two sections of angle iron mitered together. One leg of the brace is adapted, to receive the riser of a stair; and the other leg is adapted to receive the tread of the stair. A number of these braces, each designed to define one side of a step in a curved staircase, are mounted on a flat metal bar to form a flat string for the staircase. A similar flat metal bar is place in a jig at the pitch and curvature the finished staircase is intended to assume; and the formed string is placed in the jig with the two flat bars engaging each other throughout their lengths. The two bars are then welded together to form a lamination while in the jig to provide the curved horse for one side of the staircase with the laminated bars retaining the desired curve and pitch after removal from the jig. Another metal horse is similarly formed for the other side of the staircase, but in a separate jig of different curvature. After the two curved horses are installed, the treads and risers are attached to a pair of associated braces by screws inserted from beneath the metal frames.

6 Claims, 7 Drawing Figures PATENTED RAY I 5 I975 sum 1 OF PATENTEB Q 3,732,609

SHEET 2 0F 2 1 METHOD OF MAKING CURVED STAIRCASE RELATED APPLICATION This is a divisional application of application Ser. No. 734,413, for CURVED STAIRCASE FRAME AND METHOD OF MAKING, Filed June 4, 1968 now US. Pat. No. 3,616,585.

BACKGROUND The present invention relates to curved residential staircases; more particularly, it relates to a prefabricated supporting frame for a circular staircase and a method for making it.

The prevailing commercial method for making prefabricated curved staircases to be installed in a residence includes forming a laminated wood framework which is notched at right angles to provide vertical and horizontal supports to which are attached the risers and treads of the staircase after the wood laminated frames are installed on either side of the staircase.

The process for fabricating these wood horses is time-consuming, ordinarily taking of the order of 2 days for completion of the lamination process. Further, once completed, these wooden horses are bulky and relatively heavy thereby making them hard to handle by a contractor during installation. This weight factor is also a disadvantage during the fabrication process in which the framework must be maneuvered. A further disadvantage of wooden horses is that when they are stored for long periods of time, they tend to loose their curvature; and if this loss of curvature becomes excessive, the framework becomes useless for its intended purpose. With this in mind, a manufacturer will not stockpile these wood frames, but he will wait for an order and thus cause a delay in delivery.

SUMMARY The present invention contemplates prefabricating a metal framework or horse to receive the tread and risers of a curved, residential staircase. The metal horse is fabricated by forming right-angle braces of two sections of angle irons mitered and welded together. The braces (one for each step) are then welded to a first flat metal bar in adjacent relation to each other. When all of the braces are thus secured to this flat metal bar, the resultant frame takes the form of a conventional framework or stringer for a wooden staircase. A second flat metal bar, similar to the one on which the braces are welded, is placed in a parabolically-curved jig or fixture with the proper curvature and pitch as desired in the finished curved staircase. The formed metal stringer is then placed in the jig alongside the second or outer metal bar; and the two flat metal bars are welded together at spaced intervals on top and bottom.

When the combination is removed from the jig, it retains the same curvature and pitch as is defined by the jig so that the result is a permanently-curved metal framework for supporting one side of a staircase. A second framework is similarly formed; and when the two metal horses are installed, conventional treads and risers are secured to them by means of screws extending through apertures on the braces to provide a pennanent and secure mounting.

The resultant metal horse has been found to be lighter than its wooden counterpart by about 80 pounds which facilitates handling during fabrication and installation. The metal horses have been found to have the advantage that the fabrication time has been reduced from about 2 days to l to 2 hours. Further, despite long periods of storage under varying conditions of temperature and humidity, the metal horses retain their original shape thus facilitating the fabrication and storage of a number of such horses to provide a backlog without fearing their deterioration.

Other features and advantages of the present invention will be obvious to persons skilled in the art from the following detailed description of a preferred embodiment accompanied by the attached drawing wherein identical reference numerals will refer to like parts in the various views.

THE DRAWING FIG. 1 shows the fabrication of a brace;

FIG. 2 illustrates the braces welded to a fiat metal bar;

FIG. 3 illustrates two flat metal bars clamped together in a curved jig;

FIG. 4 is a perspective view of a staircase incorporating metal horses according to the present invention taken from beneath the staircase.

FIG. 5 is a detailed section view of one tread of F IG.

FIG. 6 is a side elevation of the metal horses as installed in a staircase; and

FIG. 7 is a closeup view of a portion of a finished metal horse according to the present invention.

DETAILED DESCRIPTION Referring to FIG. 1, there is shown a right-angle fixture generally designated 10 and including a flat baseboard 11 on which are securely mounted first and second rails 12 and 13. The rails 12 and 13 define a rightangle for receiving first and second sections of angle irons designated respectively 14 and 15.

The sections 14 and 15 are mitered to form a common edge between them as at 16. The sections 14 and 15 are then welded together along the mitered interface 16 to form a right-angle brace generally designated 21. The right-angle brace 21 forms a sub-frame for receiving and supporting one side of a tread (as on the angle 14) and one side of a riser on the section 15. The particular element 21 illustrated would ultimately be placed on the right-hand side of a curved staircase as viewed from the top. Each of the sections 14 and 15 are provided with apertures, as at 19 and 20 respectively, for receiving screws which are then fastened into the tread and riser of the stair.

It will be appreciated that the width of the treads of a curved staircase vary and that even for a given tread, the width will be less on that side of the tread having the smaller radius of curvature. Thus, each of the tread portions of the braces used is pre-cut according to a known design for any given staircase; and the present invention is not limited to particular dimensional details.

Turning now to FIG. 2, a number of braces formed according to the procedure described above are designated respectively 21, 22, 23 and 24. These will ultimately form supports for the lower four steps of the staircase; and as seen in the drawing, the riser portion of the brace 23 is elongated as at 23a; and a separate angle iron 25 interconnects the portion 23a of the riser 23 and the riser portion of the brace 24 of the lowest step. Thus, the framework for the lowermost step is formed into a rectangular brace including a support iron which may be screwed to the floor.

Each of the braces 21-24 is placed on a flat jig board designated 27 and including a plurality of guide blocks 28 for positioning the braces. An elongated, flat metal bar 30 is placed on the flat jig 27; and it runs along the adjacent edges of the braces 21-24. Each of the braces 2124 is then welded to the fiat bar 30 at the end of its riser portion and at the end of its tread portion. This is illustrated more clearly in FIG. 7 (although FIG. 7 shows the completed curved framework) by means of the welds at 31 and 32 securing riser portion of brace 21 to the bar 30 and the weld at 33 securing the tread portion of the brace 22 to the bar 30 and in abutment with the brace 21.

When all of the braces have thus been welded to the flat bar 30 as are necessary for completing the entire right-hand portion of the supporting frame for the staircase (assuming the staircase is to curve to the left as viewed from the top), the result resembles a flat wooden horse or stringer for a conventional straight staircase.

Turning now to FIG. 3, a second elongated, flat metal bar 35 is placed in a jig generally designated 36 and providing a curved guide surface 37 along which the bar 35 is placed. The guide surface 37 defines the parabolic curve of the finished metal horse. The jig need not be secured in place.

Next, the flat metal horse fabricated as described above is placed in the jig with the flat bar 30 lying adjacent the flat bar 35. When fabrication is completed, the bar 30 becomes an inner bar and the bar 35 becomes an outer bar. The outer bar 35 and the flat metal horse including the inner metal bar 30 are clamped in the jig 36 by means of clamps as at 38; and the inner bar and outer bar 35 are welded together at spaced intervals, designated by reference numeral 40 in FIG. 3 on both sides (i.e. top and bottom) of the two abuting contacting bars.

After the inner and outer bars have been thus welded together the clamps may be removed; and the finished metal horse may then be removed from the jig 36. It will retain the desired shape as defined by the jig. The metal horse thus formed may be stored for indefinite periods of time without loosing its shape; and it is lighter than its wooden counterpart by about eighty pounds. I

Turning now to FIG. 4, the completed right-side metal horse is generally designated by reference numeral 44. A left-side metal horse is fabricated similarly to the method described above; but this horse ordinarily has a different curvature according to the design of the staircase. The left-side horse is generally designated 45 in the drawing. It will be appreciated that the jig into which it is fit will be convex rather than concave since the straight stringer with the braces and the flat outer bar are reversed in relation to each other, and the flat bar is placed in the jig first. Preferably, the entire staircase is fabricated before shipment to the location which it will be installed; however the treads 46 and risers 47 may be secured to the tread and riser sections of the braces on location, if desired. Holes are drilled in the laminated metal bars of the horses for receiving wooden skirt boards 48 to cover the metal framework.

FIG. 5 is a detailed drawing of the construction taken through a vertical line extending through the left-side metal framework 45 of FIG. 4; and the elements of the framework shown in FIG. 5 may be correlated with those of FIG. 7 which is, of course, a view of the rightside metal framework. The corresponding reference numerals used in FIG. 5 are the same for those used in a FIG. 7 together with a prime designation indicating a counterpart. Thus, an inner flat bar is designated 30 and an outer flat bar is designated 35 The riser portion of the upper brace is designated 21'. The tread portion of a lower brace is designated 22; and a wood screw 50 extends through the tread portion of the lower brace 22' and is received in the oak tread 46. A similar wood screw 51 extends through the riser portion of the brace 22' for securing the white pine riser of the next lower stair. As can be seen in the drawing, the riser section of the brace 21' is welded to the laminated bars 30 and 35 at 31; and the laminated bars are welded together at both top and bottom (reference numeral 40').

A triangular-shaped filler piece, designated by reference numeral 51 in FIG. 5, having a width equal to the width of a laminated bars 30' and 35 is used to fill the triangular space defined by a riser and tread of one stair and the laminated strip. A laminated wooden skirt board generally designated 52, including a first section 53 and a second section 54, is attached to the metal horse and corresponds to the skirt board 48 of FIG. 4. The attachment, as described above, is by means of screws fitting through apertures in the laminated metal bar of the horse and being received in the skirt board 52.

The metal framework for the staircase of FIG. 4 as seen from the side is shown in FIG. 6 wherein, again, the metal horse having the largest radius of curvature is generally designated 44, and the metal horse having the smaller radius of curvature is generally designated 45. As will be appreciated, during the fabrication of the metal horse 45, the first flat metal bar is curved in a concave jig so that the inner metal bar containing the braces may be placed on it and welded to it; whereas in the fabrication of the metal horse 44, the first metal bar is placed in a convex jig before the inner metal bar having the braces is welded to it.

Having thus described in detail a preferred embodiment of the inventive method and structure, it will be apparent to persons skilled in the art that certain modifications may be made and that equivalent structure may be substituted for that which has been described; and it is, therefore, intended that all such modifications and equivalents be covered as they are embraced within the spirit and scope of the appended claims.

We claim:

1. A method of making a frame for a curved staircase comprising: mounting a plurality of right-angled braces along an elongated first metal bar to define the riser portions and tread portions of one side of the stairs of said staircase, forming said first metal bar into a desirable shape defined by the curvature and pitch of the staircase, contacting said first metal bar and its attached braces with a second elongated metal bar substantially throughout their lengths, and securing said first and second metal bars together along the length of the contacting bars.

2. The method of claim 1 wherein said steps of forming and contacting comprise: placing said second bar in a jig providing a curved surface defined by the desired curve of said staircase, and then contacting said second metal bar with said first metal bar substantially along their entire respective lengths.

3. The method of claim 1 wherein said step of securing comprises: welding said first and second elongated metal bars together at spaced intervals along their lengths whereby when said framework is removed from said jig, it retains the desired shape defined by said curved surface of said jig.

4. The method of claim 1 further comprising the step of forming said braces by mitering angle-irons together to provide a right-angle brace.

5. A method of forming a staircase comprising: forming first and second side metal frames according to claim 1 wherein each of said braces define at least one aperture along the tread portion thereof and an aperture along the riser portion thereof, and securing the risers and treads to their respective brace portions of said first and second metal frames by inserting a wood screw through the proper apertures of said brace and securing the same to the riser and tread.

6. In a method of fabricating a framework for a curved staircase, the steps of contacting a first metal bar formed in a curve defined by the curvature of said staircase with a second elongated metal bar substantially throughout their respective lengths; and securing said first and second metal bar together in said curved relationship substantially throughout their lengths whereby when said bars are released, they will cooperate to maintain said curved relation. 

1. A method of making a frame for a curved staircase comprising: mounting a plurality of right-angled braces along an elongated first metal bar to define the riser portions and tread portions of one side of the stairs of said staircase, forming said first metal bar into a desirable shape defined by the curvature and pitch of the staircase, contacting said first metal bar and its attached braces with a second elongated metal bar substantially throughout their lengths, and securing said first and second metal bars together along the length of the contacting bars.
 2. The method of claim 1 wherein said steps of forming and contacting comprise: placing said second bar in a jig providing a curved surface defined by the desired curve of said staircase, and then contacting said second metal bar with said first metal bar substantially along their entire respective lengths.
 3. The method of claim 1 wherein said step of securing comprises: welding said first and second elongated metal bars together at spaced intervals along their lengths whereby when said framework is removed from said jig, it retains the desired shape defined by said curved surface of said jig.
 4. The method of claim 1 further comprising the step of forming said braces by mitering angle-irons together to provide a right-angle brace.
 5. A method of forming a staircase comprising: forming first and second side metal frames according to claim 1 wherein each of said braces define at least one aperture along the tread portion thereof and an aperture along the riser portion thereof, and securing the risers and treads to their respective brace portions of said first and second metal frames by inserting a wood screw through the proper apertures of said brace and securing the same to the riser and tread.
 6. In a method of fabricating a framework for a curved staircase, the steps of contacting a first metal bar formed in a curve defined by the curvature of said staircase with a second elongated metal bar substantially throughout their respective lengths; and securing said first and second metal bar together in said curved relationship substantially throughout their lengths whereby when said bars are released, they will cooperate to maintain said curved relation. 